Aluminum alloys are one of the most widespread metals in the world. I'm not talking about ore deposits but the usage of aluminum in every aspect of human life. It is lightweight, durable and strong. It is also corrosion-resistant because of its thin oxide film that can only be melted at over a thousand degrees centigrade. Nonetheless, aluminum coatings are used a lot, the most widespread of them being painting, oxidizing and powder coating.

Why Coat Aluminum At All?

That's
a fair question since aluminum has its own protection against the aggressive
environment, why bother coating it at all?

Modern
manufacturers and customers today have much more demands towards aluminum parts
and the conditions those part have to withstand can be too much even for the
protective oxide film.

For instance, aerospace rocket covers are made of thin aluminum sheets and the temperatures they have to withstand come close to the melting point of the oxide layer. They don't teach this point but the film can easily crack because of the rapidly changing temperatures. Marine parts are submerged in a highly corrosive salt water that gradually corrodes even aluminum. Modern industry poses new challenges concerning corrosion and the answer the manufacturers have come up is an aluminum coating.

A Brief Overview Of Anodizing, Powder Coating, and Painting

Before we start comparing the three most widespread aluminum coatings, let's freshen up your memory of those techniques in case you've gotten rusty on any of the specifics.

Anodizing

Anodizing is a unique process. It doesn't administer new material to create a coating but uses the material itself. An aluminum part is put into a tank with a conducting liquid. Then, a current with low voltage and high amperage passes through the tank and the part. As a result, the oxide film thickens and becomes porous at its outer surface.

Liquid Painting

This one is the oldest conventional technique to coating virtually any material. You purchase a can of paint and a brush and you're all set. Just be sure not to exhale too much of the paint since it's a little bit toxic until it solidifies. Over the years, the market has amassed a tremendous variety of available colors. And you can mix some paints to get the tint you want too.

Aluminum Powder Coating Process

Powder Coating aluminum is the new eco-friendly way to administer paint. You would need professional equipment, namely a pneumatic gun that sprays ionized dry powder particles that stick to the surface of the aluminum part because of ionization. Then, you put the part in the oven, bake it and the powder film becomes uniform and connects both with the powder and the part.

Powder Coating Vs. Liquid Painting

Let's
compare the two similar methods first. Both can be considered painting but they
are quite different as are their respective areas of use.

Liquid
painting is your ultimate choice if you have a low budget. The reason for that
is: you don't need any equipment at all, just a brush and the paint. That makes
it perfect for low batch manufacturing. Another low budget advantage of paint
is that you can administer a thick layer of it on a bad surface finish and the
surface will become smooth.

Apart
from that, liquid paint is great for the variety of colors it offers. Powder
coatings are not even close to all the different tints you can get from the
shops and by mixing different colors.

Now,
the powder is different from the liquid paint in a lot of ways. Firstly, it
isn't toxic. However, one of the powder coating problems is, you'll still have
to wear protective gear because inhaling small paint particles in the form of
powder isn't good for your lungs.

Powder coatings are more even, they are less prone to cracking because the powered particles sinter to the base material. With liquid paint, you can get splotches and an uneven surface layer.

Anodizing Vs. Powder Coating

It
is actually not exactly correct to compare anodizing and powder coating. The
reason for that is that those two processes can complement each other. After
anodizing, the surface of the aluminum becomes more porous. You can see it by
the way the part becomes milky rather than having a shiny metal surface. These
pores are awesome for the powder particles to flow into when they are melted.

Both
the anodized aluminum colors and the powder colors are the same variety.

Both techniques create a protective layer for corrosion and wear resistance, however, the result of anodizing is much more durable since the coating is actually part of the material.

Anodizing Vs. Liquid Painting

With
painting, the pores created from aluminum anodizing films are not as useful for
the surface finish as the powder coatings. The anodized aluminum finishes are
much lower compared to the painted ones but if you need a matted texture, there
is nothing better.

Anodizing
isn't toxic as painting but it requires a lot of energy and additional
equipment so painting is obviously cheaper.

The majority of paints conduct electricity but the porous anodizing finish will decrease the conductivity of the part. You have to take it into account if you are using aluminum parts for electrical appliances.

Conclusions

Liquid Painting, Powder Coating and Anodizing each take a great niche in aluminum part protection. All of them are good for corrosion resistance and painting and powder increase the aesthetic looks of the part and increase its surface finish. Anodizing works that way only in conjunction with the powder coating. Basically, with the biggest budget, you should use both anodizing and powder to get maximum protection and even some wear resistance. Painting is great if you really want to get original with the color or if you are just starting out and don't have a lot of resources for the expensive equipment or if your batch is too low to invest in that. Just don't forget the protective gear or you can get serious headaches or even worse conditions. The Same thing is about powder coating. You don't want to inhale the powder.